Drill ship



Feb. 13, 1968 G. R. KNIGHT, JR, ETAL 3,363,509 I DRILL SHIP 6 Sheets-Sheet 1 Filed June 21, 1966 S R O I '4 n ww om v NH N HHHH. w R. N E A m M O R w w mm 7770M ATTORNEYS Feb. 13, 1968 G. R. KNIGHT, JR., ETAL DRILL SHIP 6 Sheets-Sheet 4 Filed June 21, 1965 FIG. 4.

v i F f I F a l 5 INVENTORS GEORGE R. K/V/GHT, JR, NORMA/V W PEN/V5) wzm ATTORNEYS Feb. 13, 1968 G. R. KNIGHT, JR, ETAL 3,363,509

DRILL SHIP Filed June 21, 1966 6 Sheets-Sheet 5 FIG-.5"! I i I I: MENTOR;

I GEORGER. K/v/am; JR, NORMAN l4. PENNE Y ATTORNEYS 1968 I G. R. KNIGHT, JR., ETAL 3,368,509

. DRILL SHIP 6 Sheets-Sheet 6 Filed June 21, 1965 IIIIZ:IIIII m r MW 6 a Wm m w m WR R. N M m w m m R R m w o a 6 N fl D I\ i: Z I: m n v T 7 United States Patent Ofiice 3368,59 Patented F eb. 13, 1968 3,368,509 DRILL SHIP George R. Knight, In, Port Washington, N.Y., and Norman W. Penney, Ridgewood, N.J., assignors to John J.

McMullen Associates, Inc., New York, N.Y., a corporation of New York Filed June 21, 1966, Ser. No. 559,268 9 Claims. (Cl. 1140.5)

ABSTRACT OF THE DISCLOSURE An offshore single hull drilling ship having the characteristics of a tanker provided with a vertical drill well located near the ships pitching axis and formed by four Walls spaced inward and fore and aft from adjacent longitudinal and transverse bulkheads so as not to interfere with the principal bulkhead system of the ship. A double sectioned vertically adjustable work platform is located within the well and a rail mounted hoist mechanism travels from a position over each section to a position over the main deck transferring gear therebetween. Pressure tanks, ballast water, and drill water are stored in the outboard wing tanks of the hull and mud pumps, agitators, and other equipment are located in the centralmost compartments on a mid deck or fiat. A platform above the drill well supports the derrick for drilling operations therethrough. A passive stabilizer is provided to roll stabilize the ship.

The present invention relates to a drill ship and, more particularly, to an offshore drilling vessel having characteristics of a tanker,

The advent of advanced oil prospecting techniques has greatly increased the activity of offshore oil drilling so that there is currently a need for improved offshore drilling structures and the like. In an attempt to meet this need, a deep drilling catamaran was built having a split hull, an over-all length of 278 feet, and an over-all beam of 105 feet, with a drilling derrick straddling both hulls, and conducting drilling operation through the space between the hulls. A vessel of this type is disclosed in the Maritime Reporter and Engineering News, Sept. 15, 1965, page 10. The catamaran drilling ship has not been free of problems; for'example, the short pitching period of this vessel causes it to respond to wave action which would have little or no effect on vessels with greater lengths.

The present invention provides a drill ship which has a length near or above 500 feet and contains all systems necessary to conduct the same drilling operations as carried out on land and which, unlike the stationary offshore drilling platforms, can move from one drilling location to another or which can be brought back to a port facility for maintenance.

The drill ship according to the present invention preferably has the characteristics of a tanker as described hereinbelow. As one example, reference is made to the T-Z tanker which is a somewhat commercially obsolete liquid cargo carrier, and, since it was in demand during the Second World War, there is a large number of these types of vessels registered throughout the world. The characteristics of the T-2 tanker include certain features which make it extremely desirable for use as an offshore drilling ship; For example, the longitudinal bulkhead system extends from-the hold to the main deck of the hull and substantially throughout the ships length so that the hull is divided into three or more lateral compartments. With machinery, mud tanks, and treatment sections located in the center compartment, the Wing tanks are left free for drill water and ballast storage, as well as providing space for vertically arranged pressure tanks to store mud and cement. With this arrangement, expensive machinery and treatment apparatus are protected from collision by the outboard wing tanks. Moreover, the bulkhead system of the tanker facilitates a drill well between longitudinal and transverse bulkheads without detracting from the structural function of the bulkhead system.

Although the invention is hereinafter described with reference to a T-2 type tanker with two longitudinal bulkheads, it should be understood that this is by way of example only and that other types of tankers could be converted to, or a new ship can be built as, the drill ship of the present invention.

One example of a drill ship according to the present invention has an open drill well aft but near the ships mid length to enable vertical passage of drilling gear and pipe. The skeleton framework or bulkhead system of the tanker is such that the drill well can be conveniently cut through the decks of the ship without any major reworking of the supporting structure. Immediately over this drill Well is arranged a drilling platform which supports a vertically extending retractable derrick normally used in drilling operation-s.

Longitudinally extending crane rails are provided between the platform and main deck to reinforce the platform supporting structure and to support a portable, traveling hoist above the drill well which is capable of transporting gear into and out of the well.

Also, according to the present invention, a fiat or tween-deck is arranged slightly above one-half the distance between the hold and the main deck.

The ship is also provided with mud tanks mounted on the tween-deck and located forward of the drill section, said tanks having agitators and cooperating with mud pumps to deliver mud to drilling equipment. These mud tanks are arranged near the ships longitudinal center line and are flanked by drill water or ballast compartments at the outboard sides of the vessel. Each mud tank is fitted with a motor driven agitator to prevent settling. A row of pressure tanks is mounted vertically between the main deck and hold along the outboard sides of the ship forward of the mud tank section.

Since the tanker usually has two or more longitudinal bulkheads extending the full height of the hull to divide the same into three lateral compartments, the outboard liquid-tight drill water compartments and pressure tank storage compartments are available for drilling purposes with relatively little reworking of the vessel,

Located on the main deck above the mud tank and pressure tank sections is a double row of pipe storage I racks separated by a pipe dragway which lies along the longitudinal center of the ship. A pair of cranes is supported above the main deck for general utility and is used to deliver drill pipe to the dragway where winch cables are connected to pull the pipe aft.

A passive, open channel-type stabilizer is provided aft of the drilling section of the vessel in order to stabilize the vessel in the roll plane during drilling operations and when the ship is under way. Although the tanker is a fiat bottom vessel, its roll characteristics would normally make it unsuitable for a drilling ship. However, with the open channel-type stabilizer, the ship is sufficiently stabilized to enable drilling operation.

A Work platform is suspended in the drill well, and its vertical position within the well is adjustable to facilitate the handling of drilling gear.

It is, therefore, a primary object of the present invention to provide a new and improved design for a drill ship which conveniently carries all the equipment and facilities necessary to carry out ofishore operations. It is within the purview of this object to provide a drill ship the design of which enables use of conventional drilling gear.

It is still a further object of the present invention to provide a new and improved drill ship design which has the characteristics of a tanker including a length affording a relatively lOng pitching period.

It is yet a further object of the present invention to provide a drill ship with a vertical, open drill well at approximately the pitching axis and a horizontal trackmounted platform vertically adjustable in said Well,

It is a still further object of the present invention to provide a converted tanker drill ship with a passive roll stabilizer.

Another object of the present invention is to provide a converted tanker drill ship with a drilling section, a tween-deck arranged at least forward of said drill section, a plurality of mud tanks on said tween-deck and forward of the drill section, and a mud pump section located on said tween-deck between said mud pumps and the drilling section.

A further object of the present invention is to provide a drill ship having two rows of drill pipe racks located forward of the drill section on either side of the ships center line and further provided with a dragway between said rows in order to facilitate the handling of drill pipe.

It is yet a further object of the present invention to provide a drill ship with a pair of longitudinally arranged rows of pressure tanks located in wing tanks between the main deck and hold of the ship.

Other further objects of the present invention will become apparent with the following detailed description when taken in view of the appended drawings in which:

FIGS. la and lb are side elevation views of the ship according to the present invention with parts broken away;

FIG. 2 is a top plan view of the main deck of the ship;

FIG. 3 is a horizontal section looking down onto the mid or tween-deck of the ship;

FIG. 4 is a transverse vertical section taken along line 44 of FIG. 10;

FIG. 5 is a transverse vertical section taken along line 5---5 of FIG. la;

FIG. 6 is a longitudinal vertical section taken along line 66 of FIG. 3; and

FIG. 7 is a transverse vertical section taken along line 77 of FIG. 3.

Referring now to the drawings in detail, a converted tanker generally indicated as 10 is fitted fore and aft With anchors 12 to fix the ships location during drilling operations. Each anchor line is wound on a winch drum located on the main deck which aids in digging the anchor in and keeping the anchor line tight. A drill section 14, to be further described below, is located just aft of the ships mid length, and an open channel-type stabilization tank 16 is arranged across the ships hull at a location between the engine area and drill section 14. The stabilizer is provided by cutting openings in the longitudinal bulkheads at locations between two liquid-tight transverse bulkheads. In this way, weight and space required for the stabilizer are held to a minimum, A more detailed description of suitable stabilizer designs is set forth in copending patent application Ser. No. 386,982, filed Aug. 3, 1964, by Sheldon B. Field.

Any suitable liquid, such as fresh and seawater, bunker oil, fuel, or the like, can be used for the stabilizer medium. However, it is important to fill the stabilizer with liquid to a level such that the liquid oscillation period equals the roll period of the ship. If the ships condition changes so that it rolls at a new frequency, the liquid level in the stabilizer can be adjusted accordingly. Since the vertical dimension throughout the stabilizer is a full deck height, the liquid level can be adjusted for all ship conditions and still have a free liquid surface.

In order to impart the stabilizing moment at the proper time, the openings in the longitudinal bulkheads should be dimensioned to impart enough damping to the trans- 4- ferring liquid to maintain liquid oscillation 90 behind the ships oscillation. Furthermore, openings are also preferred near the top of the longitudinal bulkheads to enable a free and unimpeded transfer of air.

In operation, the liquid in the stabilizer transfers from one end of the stabilizer to the other in response to the roll of the ship, and the timed accumulation of liquid imparts a moment to the ship in opposition to the roll thereof.

A power plant for the principal and auxiliary drilling operation is located in section of the ship, just aft of the drill well. Since the ships propulsion plant is not used for drilling, it is expected that drilling operations will be more reliable and less maintenance or down time will be required. Moreover, because of the large capacity of the ship, uninterrupted drilling can be conducted for months at a time without returning to port or depending upon a mother ship.

The forward part of the ship includes a main deck and hold and is divided by transverse bulkheads spaced along the longitudinal axis of the ship. A pair of longitudinal bulkheads extending from the hold to the main deck divides the ship into two wing compartments and a central compartment. According to the invention, a tweendeck is arranged between the main deck and hold to support drilling machinery and the like. The central compartment on the tween-deck two sections forward of the drill well supports a number of mud tanks with an agitator at the bottom of each to temporarily store mud for the drilling operation. The center section on the tween-deck between the mud tank section and the drilling section functions as a pump room and is equipped with two large mud pumps capable of delivering mud from the tanks to the drilling equipment. In the center section on the tween-deck just forward of the mud tank section, there is provided a mud mixing pump and cement unit room where the mud and cement are mixed to the proper consistency,

As better seen in FIG. 3, a pair of vertically extending pressure tanks 18 are arranged in the wing tanks of the three sections forward of the mud tank section. As seen in FIG. 1b, pressure tanks 18 extend from the hold to about the main deck and are laterally secured by braces or other suitable means. Tanks 18 are used for storing mud or bulk cement.

Drill or ballast water storage compartments (not shown) are provided in the center hold section substantially throughout the length of the vessel forward of the drill section.

As better seen in FIGS. 1b and 2, two rows of pipe storage racks 20 are arranged longitudinally on top of the main deck and forward of drill section 14. Another pipe storage rack is located along the center line forward of the double rows of storage racks also on the top of the main deck. Racks 20 include two or more rows of spaced steel pillars 21 extending upwardly from the main deck. Pipe is stacked between pillars 21 with their axes parallel to the longitudinal axis of the ship. Wooden beams 23 are attached across the tops of transversely aligned pillars 21 by any suitable means (not shown) to prevent inadvertent movement of the pipe.

Along the center line of the main deck and between the rows of racks 20, there is provided dragway having approximately a five-foot width along which the drill pipe is drawn when required for use. Racks 20 are conveniently positioned so that the pipe can be delivered to the dragway with little handling.

A pair of cranes 22 is mounted above the main deck on opposite sides of the vessel. Each crane is rotatably mounted on a supporting column 24 which extends through the main deck and can be partially supported by the tween-deck. Suitable means are provided to transmit the weight of each crane to the load bearing framework of the ship. These cranes are used for general purpose and perform various gear and pipe handling functions required for the drilling operation. For example, the cranes can be used to transfer drill pipe between ship and shore. I

The drill section 14 is located slightly aft of the ships mid length. However, alternate designs could provide drill section 14 forward of the ships mid length. But it is preferred that the drill section be located near the center of the ships pitching axis so that pitching affects the drilling operation as little as possible. Dn'll section 14 comprises a vertically extending open drill well 26 extending from the main deckdown through the hold. As better seen in FIGS. 1a and 3, drill well 26 is cut through the decks at locations between two transverse bulkheads 44 and 46 and two longitudinal bulkheads. In this way, the supporting bulkhead or framework system of the ship is unaffected by the drill well location. Four vertical walls 48, 50, 52 and 54 extend throughout the height of well 26 and have all edges welded liquid-tight to each other and to the hold of the main deck of the ship. These walls define the inner boundary of well 26 and prevent sea water from entering any other part of the ship. It is expected that, under average loading conditions, the water level in the drill well will be approximately at the mid deck level of the vessel.

A pair of tracks 36 are mounted to each 'wall 48 and 50 of drill well 26 and are arranged parallel to each other and extend from the main deck down to a location just above the tWeen-deck level. One-half of a horizontal work platform 34 is supported at its outboard edge by each pair of tracks 36. The vertical position of platform 34 is adjustable so that it can be positioned a predetermined distance above the free water surface regardless of the water line position in well 26. The inner edge of each one-half platform section 34 has a semicircular cut 38 which defines an enlarged opening through which drill pipe 40 extends. The vertical adjustability of platform 32 also facilitates various other work in the well, such as the installation and adjustment of the blowout preventer stack.

A retractable drilling derrick 30 is supported directly over drill well 26 by platform 58 which, in turn, is supported above the main deck by framework system 28. The forward legs 60 of derrick 30 are hinged to platform 58, but the rear legs 62 are stationary and cooperate with members to form an A-frame which supports winch cables (not shown) used to raise and lower derrick 30. A draw work shed 64 is also supported by platform 58 beneath the rear legs 62 of derrick 30. A pair of longitudinally extending crane rails 66 is mounted to four upright pillars 68 and 70 between the platform 58 and main deck. As better seen in FIG. 6, crane rails are arranged on opposite sides of the ships center line and have their forward parts over drill well 26 and their end parts over a part of the main deck. A traveling hoist 72 is mounted on each crane rail 66 and functions to transfer gear or equipment between the main deck and drill well 26. During operation, derrick 30 is in the vertical position shown in solid, but when the vessel is under way, derrick 30 is retracted to substantially horizontal position as shown in phantom.

Platform 74, which supports desilter, shale shaker, mud lab and other equipment to assist the drilling operation, is provided on the main deck at a position transversely aligned with derrick 30. During drilling operation, the mud is cycled up through the drilling pipe to platform 74 where it is desilted or otherwise treated. The treated mud is then fed to the top of an open trench (not shown) where it slides back to the mud tanks for reuse.

It is the intent and purpose of the present invention to provide a drill ship which enables a drilling operation that is almost identical to land-based drilling activity. After ship arrives at the drill location, anchors 12 are cast to securely moor vessel 10 relative to the ocean floor. Pitching stability is derived from the over-all length,

more than 500 feet, of the converted T-2 tanker, and roll stability is provided by stabilizer 16 so that drilling operation can proceed notwithstanding a fairly rough sea.

Derrick 30 is rotated upward from a horizontal to a vertical position, and the cranes 22 begin delivering pipe to the center dragway 15 between pipe racks 20. Mud is taken from the pressure tanks and mixed with drill water in the mud mixing pump room and delivered to the mud storage tanks which are provided with agitators to prevent settling.

Platform 32 is moved to the desired vertical position relative to the free water surface, and the drill pipe is sequentially connected in the conventional manner to extend through opening 38 in the manner described. Traveling hoist 72 moving on rails 66 is used to deliver gear from the main deck down onto platform 32 in well 26.

As the drilling operation proceeds, mud pumps 19 deliver mud from the mud tanks to the drill pipe, and the used mud is recirculated through treatment stations to the mud tanks.

It should be understood that various modifications can be made to the herein disclosed example without departing from the spirit and scope of the present invention.

What is claimed is:

1. An offshore drilling system comprising a single-hull vessel including a main deck and a hull bottom and a principal bulkhead system including two transversely spaced longitudinal bulkheads extending from the hull bottom to the main deck to form with the hull a pair of wing tanks located on outboard sides of the hull and along a substantial portion of the vessel to provide compartments for ballast water, drill water and pressure tanks, said longitudinal bulkheads being disposed symmetrically on opposite sides of the vessel centerline, and a plurality of transverse bulkheads intersecting said longitudinal bulkheads and extending from the hull bottom to the main deck and spaced longitudinally from each other so that the main bulkhead system is a symmetrical lattice configuration, an open vertical drill well formed by upstanding walls bounding all sides thereof located operatively near the pitching axis of the vessel and between two adjacent transverse bulkheads and between the longitudinal bulkheads, the fore and aft walls being spaced aft and forward respectively of the associated adjacent transverse bulkhead and the side walls being spaced inboard of said longitudinal bulkheads so as to avoid interfering with the structural integrity of the principal bulkhead system, the center of said drill Well being located generally along the center line of the vessel, drilling means including a derrick supported above the main deck and over the drill well to carry out drilling operations through said drill well.

2. A system as set forth in claim 1 further comprising a platform supported on the main deck above said well and upon which the derrick is supported, at least one rail extending longitudinally and mounted below said platform in such a way that a first part is over said well and a second part is over said main deck, a work platform within said Well, and a hoisting mechanism traveling on said rail to transfer gear between the main deck and said work platform.

3. A system as set forth in claim 2 further comprising a work platform within said well, said work platform and Well including mounting means to enable adjustment of the vertical position of said work platform.

4. A system as set forth in claim 3 wherein said work platform comprises tWo separated sections, each vertically adjustable relative to the ship, each section defining a cut such that the drill pipe extending through the drill well passes through the opening defined by the pair of cuts.

5. A system as set forth in claim 1 wherein a passive stabilizer tank is provided within said vessel, said stabilizer comprising an elongated tank having its axis transverse to the vessel and extending from one side of the hull to the other, said vessel having at least one longitudinal bulkhead dividing said tank and extending the full height of said tank, the portion of said longitudinal bulkhead within said tank having openings defined therein to enable liquid and air transfer therethrough and a body of liquid partially filling said tank to a level such that the period of liquid oscillation generally equals the roll period of the vessel, and the top of said tank being spaced above the liquid level when at rest to provide an air space above the entire liquid free surface.

6. A system as set forth in claim 1 wherein the vessel is fitted with a horizontal fiat spaced between the main deck and the hold, a plurality of mud tanks provided on said flat, each mud tank having a motor driven agitator to prevent the mud therein from settling out, and a mud pump supported on said fiat longitudinally between said mud tanks and said drill well to feed mud to the drill pipe in said well during drilling operation and a plurality of cylindrical pressure tanks mounted upwardly within said wing compartments, each pressure tank storing one of the materials bulk cement and mud; and a mud mixing system supported on said flat in the vicinity of the pressure tanks and Within said central compartments to deliver mud of predetermined consistency to said mud tanks.

7. A system as set forth in claim 1 further comprising a pair of general purpose cranes mounted above the main deck near opposite outboard sides thereof, and one of said cranes being forward of the other.

8. A system as set forth in claim 6 wherein said mud tanks are positioned forward of said drill well and near the vessels center line.

9. A system as set forth in claim 4 further comprising a platform supported on the main deck above said well and upon which the derrick is supported, a pair of parallel rails extending longitudinally and mounted below said platform each With a first part over different sections of said platform and each with a second part over said main deck, and a hoisting mechanism traveling on each rail to transfer gear between the main deck and the respective platform section.

References Cited UNITED STATES PATENTS Hilliard 114l25 MILTON BUCHLER, Primary Examiner. T. BLIX, Assistant. Examiner. 

